Vector Transmitted Zoonotic Diseases Flashcards
What is the causitive agent of plague - type of pathogen and species name
G- bacterium, Y. pestis
What are the three different types of plague? Describe each: general symptoms, mode of transmission, is it transmissible to humans
- bubonic plague: at least one swollen and painful lymph node (buboes), from infected flea bite
- septicemic plague: skin and other tissues may turn black and die, from bites of infected fleas, handling an infected animal, may develop for untreated bubonic plague
- pneumonic plague: rapidly developing pneumonia, from inhaling infectious droplets, or from untreated bubonic or septicemic plague, most serious form of the disease, can be spread from person to person
Describe the transmission cycle of plague
- sylvatic cycle: infected flea –> infects rodent –> flea or rodent transmits to domestic rodents or humans
- urban cycle: infected flea –> domestic rodent –> flea or rodent transmits to humans
- bubonic plague can develop to pneumonic plague –> transmits humans to humans
Where are plague cases in the US located? What’s the common mode of transmission to humans?
- SW USA
- fleas on dogs, infected rodents
What form of plague was most prevelant in the Madagascar outbreak? Where were the majority of cases?
- primarly pneumonic plague
- most cases were concentrated in the capital city and the main seaport
What was the first recorded mass outbreak of the plague? Where was it?
Justinian plague - Constaniople and Europe
What plague epidemic resulted in massive change to European social structure?
The black death
Where was the last plague epidemic? Describe a societal issue that occured because of this
- China –> India –> San Fransico
- chinese and indian people in San Fransico were discrimated against because of this
What treatments were used during The Black Death?
- bathing in human urine
- use of leeches
- drinking molten gold/powedered emeralds
- chopping up a snake everyday
- not sleeping during the day
Although the plague doctor gown was probably entirely useless, describe two components that might have helped reduce transmission of plague
- beak has flowers - freshness thought to eliminate bad air –> might have filtered the air
- long gown - help prevent flea or rodent bites
What are the current methods of treatment of plague?
- doxycycline, streptomycin, gentamicin, or ciprofloxacin
- supportive therapy - oxygen, fluids, and respiratory support
- patients with pneumonic plague should be strictly isolated
Describe how we prevent plague
- control of rodents and vectors: insectidices + rodenticides, focus on flea control duirng outbreaks
- vaccine available
- education
Where is the majority of malaria cases concentrated?
Africa, especially children <5yrs
What are the different malaria species? Briefly describe each
*Plasmodium vivax, falicparum, malariae, knowlesi, simlum
- vivax, falicparum, and malariae are the three main ones
- malriae likely emerged from gorillas
- knowlesi likely emerged from macaques
- simulium causes malaria in south america
What is the vector that transmits malaria (include genera name)
mosquitoes - Anopheles
What drugs are used to treat malaria?
- artemisinin - some resistance –> combination therapy
- chloroquine
- primaquine
Why does malaria attack the liver?
sporozoiotes bind to sulphur proteins, such as CSP. The liver has an abundance of sulphur molecules
Why does the recombinant malaria vaccine have HepBsAg?
malaria proteins themselves are not very immunogenic - HepBsAg helps create a T cell response
Why is there a huge gap between those who have ITNs (insecticide treated nets) and those who sleep under ITNs?
the nets get used for fishing - need to eat!
What was the largest malaria outbreak in canada?
500 men died making the Rideah Canal, 60% of the workers contracted malaria
Describe a trait that can confer partial resistance to malaria, what is an effect of this?
Sickle cell anemia - those heterozygous have partial resistance –> evolutionary pressure of malaria has resulted in 4% of west africans having this phenotype
Describe how malaria impacted racism
Ottomons were running around getting slaves. White slaves tended to die from malaria, while black slaves did better. Black slaves were placed on farms (more mosquitos). Focused on gathering black slaves over white slaves
What are the three different categories of parasitic worms, which does schistosomiasis fall into?
- nematodes (roundoworms)
- cestodes (tapeworms)
- trematodes (flatworms) - schisto
Name the species names of snails and schisto, and match the schisto species with its snail host
- snail: bulinus spp; schisto: schistosoma haematobium
- snail: biomphalaria spp; schisto: schistosoma mansoni
- snail: oncomelania spp; schisto: schistosoma japonicum
Breifly describe the life cycle of schisto, include reproduction mode
eggs –> miracidium –> snail host (where it asexually reproduces) –> free-swimming cercariae –> human host –> adult worms sexually reproduce –> eggs
What aquatic factors influence transmission of schisto?
- presence of aquatic vegetation provide excellent feeding and breeding grounds for snails
- consistent annual temperatures allow for snails to persist year round
- human activity linked to freshwater brings humans in contact with parasites - fishing, clothes washing, sand collecting, rice farming
- rainfall and flooding influences human and snail movement and behaviour
Out of the three schisto species described in class, which one(s) is/are zoonotic?
s. japonicum
Why do schisto infections in snails typically castrate the snail?
all the energy goes into reproducing the parasite
How can we tell apart S. mansoni and S. haematobium from S. japonicum
look at the eggs - S. japonicum doesn’t have a spike
What is the purpose of photoreceptors in cercariae schistos?
no humans are present at night, but during the day…swim out of snail host to find human host
Describe acute and chronic schistosomiasis
- cercaerial penetration: immediate innate response, cercariae loses tail and migrates into blood
- cercaerial dermatitis: localized itching and swelling –> red bump
- schistomulae migration: pneumonia and local inflammation in lungs
- Katayama fever: system type 1 hypersensitivity directed towards migrating schistosomulae
- anemia: adult worms cosume RBCs and absorbe large quantities of glucose
- egg production: can lead to 2nd Katayama fever event due to egg Ag sensitization
- aberrant egg migration: granulomas form around eggs that aren’t secreted (mostly in the liver)
- fibrosis, portal hypertension: due to complications with granuloma formation - eggs are the size of capillaries –> plugs them up –> fluid retention
What pathology does granuloma formation create?
hepatosplenomegaly –> enlargement of spleen and liver
What are the negative impacts due to chronic schisto? What is an overall effect of these?
- anemia
- malnutrition
- learning difficulties
keeps people in poverty
What is the treatment for schistosomiasis?
chemotherapy - praziquantel tablets
What maintains the transmission of S. japonicum? What is the biggest problem
humans and livestock - especially domestic water buffalo
Describe the history of schisto control in China
- “call to duty” - emphasized preventative medicine
- schisto lowered social status for marriage (women would not move to villages that had lots of schisto) and army recuitment (better economic status, could not join army if had schisto)
- Chinese government placed lots of emphasis on snail control (molluscidies) and funded mass chemotherapy
- The Great Leap Forward: public health anti-schisto campaign - reclaimed swampland (buried snails, burned grass, built drainage ditches, and applied chemicals) and built/repaired latrines
What did the schisto control measures by the Chinese result in?
- reduced snail habitats
- reduction in infected livestock and infections in farmers
What are 4 factors that created a challenge for schisto control in China?
- Oncomelania snails are amphibious and can survive periods of droughts
- molluscidies are harmful environmental pollutants (although safe in the right amounts)
- praziquantel is the only widely available and most effect drug - worries about drug resistance, compliance is erratic, does not prevent re-infection
- S. japonicum can ultilize many different hosts to maintain infection within the environment
What were two water management projects that impacted schisto in China?
- Three Gorges Dam
- Return Land to Lake Program
Three Gorges Dam
What two regions were impacted by the dam? How were they affected?
- reservoir area upstream of the dam - not an endemic region, but fluctuating water levels impact surrouding areas and can create side pools that serve as snail breeding grounds
- downsteam of the dam - endemic and past flooding has created significant tranmission hotspots
Return Land to Lake Program
How has this program affected schisto transmission?
region used to flood regularly –> removed agriculture from the region –> more suitable snail habitat –> increase in human infection
What are the current control efforts for schisto?
- risk mapping/surveillance
- vaccine devlopment for bovines and humans
- government provided new farm equipment - farmers spend less time in water
- mass drug administration programs
Why is schistosome hybridization an emerging problem?
- diesease that are not typically zoonotic can become zoonotic via hybridization
- treatment plans focusing only on humans may no longer be viable
- differences in morbitidity
- greater fecundity, faster maturation rates, wider intermediate host spectrum
What causes the swimmer’s itch rash? How can secondary infections arise from this?
- rash: cercarial dermatitis
- exessive scratching can lead to secondary bacterial infection
What are the characteristics of beaches in the province that receive the fewest schisto reports?
- best maintained
- well located
- little vegetation near significant water movement
- water most often moves away from beach
